The present invention relates to disk tiller blades, particularly reverse-dish blades for a rotary tiller.
Tillage is the working of the soil in order to change its structure, kill weeds, or the like. It may be desirable to change the structure of the soil in order to facilitate the storage of moisture and generally enable maximum growth. Weeds may rob a crop of water, nutrients and light and are therefore generally undesirable.
A number of implements are known in the art for manipulating the soil. Plows are dragged through the earth, thereby manipulating it. The shape of the plow blade tends to cut a trench, or furrow, throwing to one side the soil that was in the trench. Since the plow is dragged through the soil and since the soil is thrown laterally with respect to the direction of motion of the plow, a great deal of energy is needed to pull it.
Disk tillers are also known in the art employing round concave disks which rotate about a shaft. The rolling of the disks through the soil tends to push the soil in one direction. Since the disks rotate through the soil, instead of being dragged, the energy necessary to pull a disk tiller is less than the energy necessary to pull a plow. However, a great deal of energy is still necessary to move the soil laterally.
Since disk tillers tend to push the soil to one side, it is common to drag two axles of disks, the second axle pushing the dirt in a direction opposite to that of the first axle. The large quantity of energy necessary to move the axles of disks through the soil requires that the tractor burn a great deal of fuel to accomplish the tilling.
Furthermore, it has been determined that excessive tillage tends to break down the structure of the soil so that the average soil particle size becomes very small. Upon the occurrence of a rainfall, the small particle size leads to caking which prevents water penetration. Thus, the concept of minimum tillage has gained acceptance. The idea is to till the soil to the minimum extent necessary to prepare the soil for seeding. Tilling methods that push the soil laterally, such as plowing and conventional disk tilling, tend to overwork the soil, thus causing the soil structure to break down. Furthermore, such conventional methods tend to leave the smaller soil particles on the surface, thus increasing the undesired caking action.
U.S. Pat. No. 2,503,993 to Blomgren discloses disk tiller blades having concavo-convex or "dished" contours facing in opposite directions on opposite halves of each of the blades. However, it is still clear that the soil is thrown at least partially in a lateral direction. The degree of "concaveness" in the Blomgren device is restricted by the physical limitation of shaping half of a disk to a dished shape. This design limits effectiveness in four ways. First, a significant amount of energy is required to move the soil laterally. Second, the Blomgren device tends to form furrows. Third, the soil tends to break down as a result of overworking, thereby leading to caking and puddling. Fourth, the degree of "concaveness" of the blade portions determines the width of the cut. Due to the physical limitations described above, the cut of these blades has a definite limit.
U.S. Pat. No. 2,029,872 to Johnson discloses a field tiller having irregularly shaped dished rotary blades. These blades make pits or holes in the ground at regular intervals to reduce wind or water erosion. Although the use of this field tiller will reduce the degree to which the soil is worked, the use of this device produces uneven results.
The following U.S. Patents disclose tiller blades with an irregular shape:
U.S. Pat. No. 2,164,214--Lindgren PA1 U.S. Pat. No. 2,539,053--Blackledge PA1 U.S. Pat. No. 420,403--Boyer PA1 U.S. Pat. No. 1,058,140--Beene PA1 U.S. Pat. No. 2,691,933-Emerson